fix: study-mode checkbox wasn't visible or bound (wrong RmlUi flow)rewrite

The checkbox used data-value (binds the element's 'value' string attribute)
instead of data-checked (binds the 'checked' bool state) -- per RmlUi docs,
checkboxes must use data-checked with a bool. So it neither reflected nor
toggled study_mode, and with no explicit styling it rendered invisibly.

Fix: wrap the input in a <form> (canonical RmlUi form-control flow), switch
data-value -> data-checked, and give #cb-study an explicit visible style
(border + background, green fill when :checked). Verified the document loads
with no RmlUi parse errors.

Note: RmlUi's border shorthand is 'width color' (no 'solid' keyword).

1 files changed, 6 insertions, 4 deletions

diff --git a/game/study_player/ui/main.rml b/game/study_player/ui/main.rml
index 821293e..f6bc5fe 100644
--- a/game/study_player/ui/main.rml
+++ b/game/study_player/ui/main.rml
@@ -57,10 +57,12 @@
     <!-- ================================================================ -->
     <div id="bottom-bar">
         <div id="help-text">{{help_text}}</div>
-        <div id="study-mode-box">
-            <input type="checkbox" id="cb-study" data-value="study_mode"/>
-            <span id="study-label">Study Mode</span>
-        </div>
+        <form id="study-form">
+            <div id="study-mode-box">
+                <input type="checkbox" id="cb-study" data-checked="study_mode"/>
+                <span id="study-label">Study Mode</span>
+            </div>
+        </form>
     </div>
 
     <!-- ================================================================ -->